Heart valve prosthesis

ABSTRACT

A heart valve prosthesis configured for deployment within a native heart valve. The heart valve prosthesis includes a tubular stent and a prosthetic valve component disposed within and secured to the stent. In addition, at least two positioning elements are coupled to a distal end of the stent to position and anchor the prosthesis within the native heart valve. Each positioning element transforms from a compressed configuration in which the positioning elements distally extend from the distal end of the stent to a deployed configuration in which the positioning elements proximally extend from the distal end of the stent. Each positioning element includes at least one U-shaped or V-shaped support arm that bends radially outward and then towards an outer surface of the stent such that it translates more than ninety degrees from the compressed configuration. Each positioning element may include an outer support arm and an inner support arm.

FIELD OF THE INVENTION

The present invention is directed to a valve prosthesis havingpositioning elements for positioning and anchoring the prosthesis at atarget location and a method of percutaneously delivering the prosthesisto the target location.

BACKGROUND OF THE INVENTION

A wide range of medical treatments are known that utilize “endoluminalprostheses.” As used herein, endoluminal prostheses are intended to meanmedical devices that are adapted for temporary or permanent implantationwithin a body lumen, including both naturally occurring and artificiallymade lumens. Examples of lumens in which endoluminal prostheses may beimplanted include, without limitation: arteries, veins gastrointestinaltract, biliary tract, urethra, trachea, hepatic and cerebral shunts, andfallopian tubes. Stent prostheses are known for implantation within abody lumen for providing artificial radial support to the wall tissuethat defines the body lumen. To provide radial support to a bloodvessel, such as one that has been widened by a percutaneous transluminalcoronary angioplasty, commonly referred to as “angioplasty,” “PTA” or“PTCA”, a stent may be implanted in conjunction with the procedure.Under this procedure, the stent may be collapsed to an insertiondiameter and inserted into the vasculature at a site remote from thediseased vessel. The stent may then be delivered to the desiredtreatment site within the affected vessel and deployed, byself-expansion or radial expansion, to its desired diameter fortreatment.

Recently, flexible prosthetic valves supported by stent structures thatcan be delivered percutaneously using a catheter-based delivery systemhave been developed for heart and venous valve replacement. Theseprosthetic valves may include either self-expanding orballoon-expandable stent structures with valve leaflets attached to theinterior of the stent structure. The prosthetic valve can be reduced indiameter, by crimping onto a balloon catheter or by being containedwithin a sheath component of a delivery catheter, and advanced throughthe venous or arterial vasculature. Once the prosthetic valve ispositioned at the treatment site, for instance within an incompetentnative valve, the stent structure may be expanded to hold the prostheticvalve firmly in place. One example of a stented prosthetic valve isdisclosed in U.S. Pat. No. 5,957,949 to Leonhardt et al. entitled“Percutaneous Placement Valve Stent”, which is incorporated by referenceherein in its entirety. Another example of a stented prosthetic valvefor a percutaneous pulmonary valve replacement procedure is described inU.S. Patent Application Publication No. 2003/0199971 A1 and U.S. PatentApplication Publication No. 2003/0199963 A1, both filed by Tower, etal., each of which is incorporated by reference herein in its entirety.Minimally invasive and percutaneous replacement of cardiac valvestypically does not involve actual physical removal of the diseased orinjured heart valve. Rather, the replacement stented prosthetic valve isdelivered in a compressed condition to the valve site, where it isexpanded to its operational state.

A human heart includes two atrio-ventricular valves through which bloodflows from the atria to the ventricles, the valves functioning toprevent return of blood to the atrium. The tricuspid valve, also knownas the right atrioventricular valve, is a tri-flap valve located betweenthe right atrium and the right ventricle. The mitral valve, also knownas the bicuspid or left atrioventricular valve, is a dual-flap valvelocated between the left atrium (LA) and the left ventricle (LV), andserves to direct oxygenated blood from the lungs through the left sideof the heart and into the aorta for distribution to the body. As withother valves of the heart, the mitral valve is a passive structure inthat it does not itself expend any energy and does not perform anyactive contractile function. The mitral valve includes two moveableleaflets that each open and close in response to differential pressureson either side of the valve. Ideally, the leaflets move apart from eachother when the valve is in an open position, and meet or “coapt” whenthe valve is in a closed position. Problems that may develop with valvesinclude stenosis in which a valve does not open properly, and/orinsufficiency or regurgitation in which a valve does not close properly.Stenosis and insufficiency may occur concomitantly in the same valve.The effects of valvular dysfunction vary, with mitral regurgitation orbackflow typically having relatively severe physiological consequencesto the patient.

Due to the different physical characteristics of the mitral valve ascompared to other valves such as the pulmonary valve, percutaneousimplantation of a valve in the mitral position has its own uniquerequirements for valve replacement. There is a continued desire toimprove mitral valve replacement devices and procedures to accommodatethe structure of the heart, including by providing improved devices andmethods for replacing the mitral valve percutaneously.

BRIEF SUMMARY OF THE INVENTION

Embodiments hereof relate to a heart valve prosthesis that includes atubular stent and a prosthetic valve component disposed within andsecured to the stent. The stent has a compressed configuration fordelivery within a vasculature and a deployed configuration fordeployment within a native heart valve. In addition, at least twopositioning elements are coupled to a distal end of the stent toposition and anchor the prosthesis within the native heart valve. Eachpositioning element includes an outer U-shaped or V-shaped support armand an inner U-shaped or V-shaped support arm that both distally extendfrom the distal end of the stent when the stent is in the compressedconfiguration. During deployment of the prosthesis, each support armbends radially outward and then towards an outer surface of the stentsuch that it translates more than ninety degrees from the compressedconfiguration to proximally extend from the distal end of the stent whenthe stent is in the deployed configuration.

According to another embodiment hereof, a heart valve prosthesisincludes a tubular stent and a prosthetic valve component disposedwithin and secured to the stent. The stent has a compressedconfiguration for delivery within a vasculature and a deployedconfiguration for deployment within a native heart valve. In addition,at least two positioning elements are coupled to a distal end of thestent to position and anchor the prosthesis within the native heartvalve. Each positioning element is attached to the stent by two V-shapedconnectors such that there are four connection points between eachpositioning element and the stent. Each positioning element includes aU-shaped or V-shaped support arm that is approximately parallel with alongitudinal axis of the stent and distally extends from the distal endof the stent when the stent is in the compressed configuration. Duringdeployment of the prosthesis, each positioning element bends radiallyoutward and then towards an outer surface of the stent such that thesupport arm translates between 135 degrees and 180 degrees from thecompressed configuration to proximally extend from the distal end of thestent when the stent is in the deployed configuration.

Embodiments hereof also relate to a method of percutaneously deliveringand deploying a prosthetic valve within a native mitral valve. Aprosthetic valve delivery system is tracked through the vasculature tothe native mitral valve. The prosthetic valve delivery system includes avalve prosthesis having a tubular stent, a prosthetic valve componentdisposed within and secured to the stent, and at least two positioningelements coupled to a distal end of the stent, the two positioningelements each having an outer U-shaped or V-shaped support arm and aninner U-shaped or V-shaped support arm that both distally extend fromthe distal end of the stent when the stent is in a compressedconfiguration for delivery. An outer sheath of the prosthetic valvedelivery system is retracted to expose the positioning elements, whereineach support arm bends radially outward and then towards an outersurface of the stent such that it translates more than ninety degreesfrom the compressed configuration to proximally extend from the distalend of the stent and press against the native mitral valve and/or theleft ventricular wall in order to position the valve prosthesis. Theouter sheath is further retracted to expose the stent, thereby allowingthe stent to self-expand into a deployed configuration.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of embodiments hereof asillustrated in the accompanying drawings. The accompanying drawings,which are incorporated herein and form a part of the specification,further serve to explain the principles of the invention and to enable aperson skilled in the pertinent art to make and use the invention. Thedrawings are not to scale.

FIG. 1A and FIG. 1B are schematic side and top views, respectively, of avalve prosthesis having positioning elements according to an embodimenthereof, wherein the valve prosthesis is in a delivery or compressedconfiguration with positioning elements distally extending from a distalend of the prosthesis.

FIG. 2A and FIG. 2B are schematic side and top views, respectively, ofthe valve prosthesis of FIG. 1A and FIG. 1B, wherein the valveprosthesis is in an expanded or deployed configuration with positioningelements proximally extending from a distal end of the prosthesis.

FIG. 3 is a side view illustration of an exemplary stent that may beutilized in the valve prosthesis of FIG. 1A and FIG. 1B, wherein thestent is in a delivery or compressed configuration.

FIG. 4 is a side view illustration of the exemplary stent of FIG. 3,wherein the stent is in an expanded or deployed configuration.

FIG. 5 is an isometric view illustration of the exemplary stent of FIG.3, wherein the stent is in an expanded or deployed configuration andincludes a prosthetic valve located therein.

FIG. 6 is a side view illustration of the exemplary stent of FIG. 3,wherein the stent is in an expanded or deployed configuration andpositioned within at a mitral valve of a heart.

FIGS. 7A and 7B illustrate side and end views, respectively, of a valveprosthesis in an unexpanded or delivery or compressed configuration,loaded into a delivery system, according to an embodiment hereof.

FIGS. 8-10 illustrate side views of the valve prosthesis of FIG. 7,wherein a sheath of the delivery system is progressively retracted toexpose the positioning elements of the valve prosthesis.

FIGS. 11-12 illustrate side views of the valve prosthesis of FIG. 7,wherein a sheath of the delivery system is progressively retracted toexpose the stent of the valve prosthesis.

FIG. 13 illustrates a side view of the valve prosthesis of FIG. 7 in anexpanded or deployed configuration, after release from the deliverysystem.

FIG. 14 is a side-view illustration of a portion of the valve prosthesisof FIG. 1, wherein each positioning element is coupled to the stent atfour connection points.

FIG. 15 is a cross-sectional view taken along line X-X of FIG. 14.

FIG. 16 through FIG. 20 illustrates a method of implanting a valveprosthesis at a mitral valve target location within a heart, accordingto an embodiment hereof.

FIG. 21A and FIG. 21B are schematic side and top views, respectively, ofa valve prosthesis having positioning elements with outer and innerU-shaped support arms according to an embodiment hereof, wherein thevalve prosthesis is in a delivery or compressed configuration withpositioning elements distally extending from a distal end of theprosthesis.

FIG. 22A and FIG. 22B are schematic side and top views, respectively, ofthe valve prosthesis of FIG. 21A and FIG. 21B, wherein the valveprosthesis is in an expanded or deployed configuration with positioningelements proximally extending from a distal end of the prosthesis.

FIGS. 23A and 23B illustrate two side views of a valve prosthesis havingpositioning elements with outer and inner U-shaped support armsaccording to an embodiment hereof, wherein the support arms extend fromdistalmost crowns of the valve prosthesis and the valve prosthesis is inan expanded or deployed configuration.

FIG. 23C is an enlarged view of a portion of the valve prosthesis ofFIG. 23A.

FIGS. 24A and 24B illustrate two side views of a valve prosthesis havingpositioning elements with outer and inner U-shaped support armsaccording to an embodiment hereof, wherein the support arms extend frombetween the distalmost crowns of the valve prosthesis and the valveprosthesis is in an expanded or deployed configuration.

FIG. 24C is an enlarged view of a portion of the valve prosthesis ofFIG. 24A.

FIG. 25A is a side view of a valve prosthesis having positioningelements with triple U-shaped support arms according to an embodimenthereof, wherein the valve prosthesis is in an expanded or deployedconfiguration.

FIG. 25B is an enlarged view of a portion of the valve prosthesis ofFIG. 25A.

FIGS. 26A-26F illustrates various configurations of generally U-shapedor V-shaped support arms according to embodiments hereof.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described withreference to the figures, wherein like reference numbers indicateidentical or functionally similar elements. The terms “distal” and“proximal” are used in the following description with respect to aposition or direction relative to the treating clinician. “Distal” or“distally” are a position distant from or in a direction away from theclinician. “Proximal” and “proximally” are a position near or in adirection toward the clinician. In addition, as used herein, the terms“outward” or “outwardly” refer to a position radially away from alongitudinal axis of the stent and the terms “backward” or “backwardly”refer to the relative transition from a proximal position to a distalposition.

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Although the description of the invention is in the contextof treatment of heart valves such as the mitral valve, the invention mayalso be used in any other body passageways where it is deemed useful.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Embodiments hereof are related to a valve prosthesis configured forplacement at a mitral valve in the heart that lies between the leftatrium (LA) and the left ventricle (LV). More particularly, a valveprosthesis 100 is shown in its compressed or delivery configuration inthe side views of FIG. 1A and FIG. 1B and in its expanded or deployedconfiguration in the side views of FIG. 2A and FIG. 2B. Valve prosthesis100 includes a framework or stent 102, a valve component 116 attachedwithin the interior portion of stent 102, and at least two positioningelements 120. As will be explained in more detail herein, eachpositioning element 120 bends or rotates more than ninety degrees withrespect to its compressed, delivery configuration during deployment ofvalve prosthesis 100. In one embodiment, each positioning element 120rotates between 135 degrees and 180 degrees during deployment of valveprosthesis 100. In the delivery configuration of FIG. 1A and FIG. 1B,each positioning element 120 distally extends from a distal end 104 ofstent 102. When released from a delivery sheath (not shown in FIG. 1A orFIG. 1B), each positioning element 120 gradually bends outwardly andthen towards an outer surface of the delivery device or stent until itreaches its deployed configuration of FIG. 2A and FIG. 2B in which eachpositioning element 120 proximally extends from distal end 104 of stent102. Once deployed, positioning elements 120 function to position andanchor valve prosthesis 100 at a native mitral valve target site. Whendeployed at a native mitral valve target site, theconfiguration/structure of a valve prosthesis as well as the deliverysystem and method of use must accommodate the size of the left ventricleand refrain from obstructing the left ventricular outflow tract Byrotating from an initial distally-extending configuration to a finalproximally-extending configuration, positioning elements 120 areparticularly configured to be deployed within a native mitral valvetarget site as will be explained in more detail below.

Stent 102 of valve prosthesis 100 is a generally tubular expandable bodyhaving a stepped profile extending between a proximal end 106 and distalend 104. As shown in the deployed configuration of FIG. 2A and FIG. 2B,stent 102 includes a distal or ventricular segment 108 having anexpanded diameter D_(V) and a proximal or atrial segment 110 having anexpanded diameter D_(A) which is greater than diameter D_(V). Whenplaced at a native mitral valve target site, ventricular segment 108extends into the left ventricle and atrial segment 110 extends into theleft atrium. Each segment of stent 102, i.e., ventricular segment 108and/or atrial segment 110, may be designed with a number of differentconfigurations and sizes to meet the different requirements of thelocations in which it may be implanted. Each segment of stent 102, i.e.,ventricular segment 108 and/or atrial segment 110, may have the same ordifferent cross-section which may be for example circular, ellipsoidal,rectangular, hexagonal, square, or other polygonal shape, although atpresent it is believed that circular or ellipsoidal may be preferablewhen the valve prosthesis is being provided for replacement of themitral valve.

In embodiments hereof, stent 102 may be made from stainless steel, apseudo-elastic metal such as a nickel titanium alloy or Nitinol, or aso-called super alloy, which may have a base metal of nickel, cobalt,chromium, or other metal. Stent 102 is self-expanding to return to anexpanded deployed state from a compressed or constricted delivery state.“Self-expanding” as used herein means that stent 102 has a mechanicalmemory to return to the expanded or deployed configuration. Mechanicalmemory may be imparted to the wire or tubular structure that forms stent102 by thermal treatment to achieve a spring temper in stainless steel,for example, or to set a shape memory in a susceptible metal alloy, suchas nitinol, or a polymer, such as any of the polymers disclosed in U.S.Pat. Appl. Pub. No. 2004/0111111 to Lin, which is incorporated byreference herein in its entirety. For self-expanding stent structures,one example of a delivery system that can be used includes a catheterwith a retractable sheath that covers and compresses the stent and itsassociated valve structure until it is to be deployed, at which pointthe sheath can be refracted to allow the stent frame to assume itsexpanded or deployed configuration. Further details of such a deliveryprocess for delivering stented valve prostheses as described herein arediscussed in further detail below.

As shown in FIGS. 3-6, stent 302 has a lattice configuration 314, withconnectors 303 extending from an end of stent 302 for connecting to adelivery system (not shown). Stent 302 is shown in a compressedconfiguration and deployed configuration in FIG. 3 and FIG. 4,respectively. Similar to stent 102, stent 302 includes an expandablebody having a stepped outer diameter formed by a distal or ventricularsegment 408 having an expanded diameter D_(V) and a proximal or atrialsegment 410 having an expanded diameter D_(A) which is greater thandiameter D_(V). Stent 302 is shown deployed at a native mitral valvetarget site in FIG. 6, with ventricular segment 408 extending into theleft ventricle and atrial segment 410 extending into the left atrium.Stent 302 is a unitary integral structure formed from a single tubularcomponent. Lattice configuration 314 of stent 302 may be produced bymachining or laser cutting the stent from a metal tube, as is commonlyemployed in the manufacturing of stents. Lattice configuration 314includes disconnected or decoupled turns or crowns 312 at the transitionarea between ventricular segment 408 and atrial segment 410, whichadvantageously allows leaflets of a valve component 516 to extend intoatrial segment 410 (and into the left atrium when in situ) as shown inFIG. 5 rather than be solely located on the outflow or ventricularsegment 408 of stent 302 (and into the left ventricle in situ). Bylocating a portion of the valve leaflets in the left atrium, therequired length of ventricular segment 408 is minimized and the lengthof the stent that protrudes into the left ventricle may be reduced.Further description of stent 302 and advantages thereof are described inco-pending patent application, U.S. application Ser. No. 13/278,050filed Oct. 20, 2011 . Although stent 102 is shown with a latticeconfiguration, it will be understood by those of ordinary skill in theart that the body of stent 102 may have any configuration or patternsuitable for placement at a native mitral valve target site.

As mentioned above, a stent of valve prosthesis 300 may be laser cutfrom a solid component of self-expanding material such that the stent isan integral structure that does not include individual components. Asingle integral structure allows the stent to be crimped or compressedto a low delivery profile. Alternatively, rather than being laser cut,the stent may be formed using any of a number of different methods thatwould be apparent to one of ordinary skill in the art such as connectingindividual annular stent struts together, chemical etching, or anothermethod of cutting a desired shape from a solid component.

Referring back to FIGS. 1A, 1B, 2A, and 2B, valve prosthesis 100includes prosthetic valve component 116 within the interior of stent 102which is capable of blocking flow in one direction to regulate flowthere through. Prosthetic valve component 116 includes valve leafletsconstructed of pericardium material and may form a bicuspid, tricuspid,or tubular replacement valve. FIG. 1A, FIG. 1B, FIG. 2A, and FIG. 2Billustrate an exemplary bicuspid valve having two leaflets 118A, 118B,although a tricuspid leaflet configuration may alternatively be used inembodiments hereof.

Valve leaflets 118A, 118B are sutured or otherwise securely andsealingly attached to the interior surface of stent 102 and/or graftmaterial (not shown) enclosing or lining stent 102 as would be known toone of ordinary skill in the art of prosthetic tissue valveconstruction. The graft material may be a low-porosity woven fabric,such as polyester, Dacron fabric, or PTFE, which creates a one-way fluidpassage when attached to the stent. In one embodiment, the graftmaterial may be a knit or woven polyester, such as a polyester or PTFEknit, which can be utilized when it is desired to provide a medium fortissue ingrowth and the ability for the fabric to stretch to conform toa curved surface. Polyester velour fabrics may alternatively be used,such as when it is desired to provide a medium for tissue ingrowth onone side and a smooth surface on the other side. These and otherappropriate cardiovascular fabrics are commercially available from BardPeripheral Vascular, Inc. of Tempe, Ariz., for example. In anotherembodiment, the graft material could also be a natural material such aspericardium or another membranous tissue such as intestinal submucosa.

As described above, leaflets 118A, 118B may be made of pericardialmaterial; however, the leaflets may instead be made of another material.Natural tissue for replacement valve leaflets may be obtained from, forexample, heart valves, aortic roots, aortic walls, aortic leaflets,pericardial tissue, such as pericardial patches, bypass grafts, bloodvessels, intestinal submucosal tissue, umbilical tissue and the likefrom humans or animals. Synthetic materials suitable for use as leaflets118A, 118B include DACRON® polyester commercially available from InvistaNorth America S.A.R.L. of Wilmington, Del., other cloth materials, nylonblends, polymeric materials, and vacuum deposition nitinol fabricatedmaterials. One polymeric material from which the leaflets can be made isan ultra high molecular weight polyethylene material commerciallyavailable under the trade designation DYNEEMA from Royal DSM of theNetherlands. With certain leaflet materials, it may be desirable to coatone or both sides of the leaflet with a material that will prevent orminimize overgrowth. It is further desirable that the leaflet materialis durable and not subject to stretching, deforming, or fatigue.

Positioning elements 120 will now be described in more detail. Referringalso to FIG. 26A, positioning elements 120 are generally shown in thefigures as being a wire or tubular structure formed into a U-shaped orgenerally U-shaped configuration such that each positioning element hastwo straight side segments 2680A, 2682A with a bottom curved segment2684A. As will be understood by those of ordinary skill in the art,“side” and “bottom” are relative terms and utilized herein forillustration purposes only. The straight side segments may be parallelto each other as shown in FIG. 26A, or may be slanted or angled awayfrom each other as shown in FIG. 26B in which two straight slanted sidesegments 2680B, 2682B flare apart as they extend from bottom curvedsegment 2684B. As utilized herein, “generally” U-shaped includes wire ortubular structures formed into: a horseshoe shape as shown in FIG. 26Cin which two curved side segments 2680C, 2682C have ends that convergetogether as they extend from bottom curved segment 2684C; a semi-circle2620D as shown in FIG. 26D; and an oblong shape 2620F as shown in FIG.26F in which two parallel straight side segments 2680F, 2682F have astraight bottom segment 2684F therebetween. In another embodimenthereof, the positioning elements may be generally V-shaped as shown inFIG. 26E in which two straight slanted side segments 2680C, 2682C areconnected together by a curved apex 2684E. The positioning elements maybe considerably longer, shorter, wider, or narrower than shown. In anycase, the positioning elements are preferably configured to be a shapeand size that can provide a positioning function and an anchoringfunction for valve prosthesis 100 when the prosthesis is deployed at anative valve target site. For example, if valve prosthesis 100 ispositioned within the native mitral valve annulus, the positioningelements extend from stent 102 on the ventricular or outflow side of themitral valve and provide interference with the native valve leafletsand/or the walls of the left ventricle, thereby inhibiting motion ofvalve prosthesis 100.

Each positioning element 120 rotates and transforms from thedistally-extending compressed configuration to proximally-extendingdeployed configuration. FIG. 7A and FIG. 7B illustrate side and endviews, respectively, of a valve prosthesis 700 in an compressed ordelivery configuration sized for delivery to the target site, loadedinto a delivery system 730. Valve prosthesis 700 includes a tubularframe or stent 702 which is similar to stent 302 described above, avalve (not shown in FIGS. 7-13 for illustrative purposes) attachedwithin the interior portion of stent 702, and two positioning elements720. In the compressed or delivery configuration, each positioningelement 720 is approximately parallel with a longitudinal axis L_(a) ofstent 702 and distally extends from a distal end 704 of stent 702.Delivery system 730 includes a catheter 732 and an outer retractablesheath or tube 734. Valve prosthesis 700 is mounted over an inner shaft736 of catheter 732 at the distal end thereof and sheath 734 surroundsand constrains valve prosthesis 700 in the compressed configuration. Inone embodiment, catheter 732 may also include a retainer 738 whichtemporarily secures proximal end 706 of stent 702 onto catheter 732. Forexample, retainer 738 may include an end stent capture configuration asdescribed in U.S. Patent Pub. 2009/0276027 to Glynn, which is herebyincorporated by reference herein in its entirety.

In order to begin deployment of valve prosthesis 700, sheath 734 isretracted in a proximal direction to expose and release positioningelements 720 as shown in FIG. 8. Upon initial release from sheath 734,positioning elements 720 flare or spread outwardly from the distal endof stent 702 such that positioning elements 720 form an acute angle Øwith respect to longitudinal axis L_(a).

As sheath 734 is further retracted, positioning elements 720 continue tobe exposed and continue to bend backwards towards the outer surface ofsheath 734 and stent 702. Notably, as positioning elements 720 arereleased from sheath 734, stent 702 remains constrained within sheath734. FIG. 9 illustrates positioning elements 720 approaching atransverse reference axis 935 between the initial distally-extendingcompressed configuration and the final proximally-extending deployedconfiguration. Transverse reference axis 935 as utilized hereindescribes an imaginary reference line that extends approximately ninetydegrees or perpendicular to the longitudinal axis La of stent 702. FIG.10 illustrates positioning elements 720 after passing over thetransverse reference axis 935, with positioning elements 720 fullyexposed or released from sheath 734 while stent 702 is still compressedwithin sheath 734. One particular feature of positioning elements 720 isapparent when comparing FIG. 9 and FIG. 10. Positioning elements 720bend or curve gradually backwards such that distal portions or tips 950of positioning elements 720 pass over the transverse reference axis 935before proximal portions or bases 952 of positioning elements 720. Afterdistal tips 950 of positioning elements 720 pass or cross over thetransverse reference axis 935 and are pointing in a proximal direction,proximal bases 952 of positioning elements 720 approach the transversereference axis 935 as shown in FIG. 10. Stated another way, distal tips950 of each positioning element 720 bend past transverse reference axis935 prior to proximal bases 952 of each positioning element 720. Due tothe above-described flaring or expanding sequence in which positioningelements 720 curve backward, the length of positioning elements 720 maybe greater than if both the proximal and distal portions of thepositioning elements crossed over the transverse reference axis 935 atthe same time, i.e., if the positioning elements were straight andextended generally parallel to the transverse reference axis 935 duringdeployment. In addition, since stent 702 is still compressed withinsheath 734, it can be observed that the length of positioning elements720 may be greater than if stent 702 was released from sheath 734 and ina deployed configuration. Accordingly, the length of positioningelements 720 is maximized which increases their ability to anchor valveprosthesis 700 when it is positioned to replace a valve. In oneembodiment in which valve prosthesis 700 is positioned at a mitralvalve, the length of each positioning element 720 is between 10 and 12mm.

FIG. 11 and FIG. 12 illustrate the continued deployment of valveprosthesis 700. Sheath 734 continues to be proximally retracted,exposing self-expanding stent 702 such that stent 702 is released toassume its deployed configuration. Sheath 734 is proximally retracteduntil proximal end 706 of stent 702 is exposed and allowed toself-expand, thereby uncoupling from retaining tip 738 of catheter 732.FIG. 13 illustrates the final deployed configuration of valve prosthesis700, in which each positioning element 720 proximally extends from adistal end 704 of stent 702. As previously described, the backwardsrotation that occurs during deployment results in each positioningelement 720 translating more than ninety degrees from its compressed,delivery configuration. During deployment, each positioning element 720essentially deploys or translates in an arc path that extends between 90and 180 degrees from the initial compressed configuration and the finaldeployed configuration. In the embodiment of FIG. 13 shown ex vivo, eachpositioning element 720 bent or rotated approximately 180 degreesbetween the initial distally-extending compressed configuration and thefinal proximally-extending deployed configuration. However, whenpositioned in vivo, tissue such as native valve leaflets may besandwiched between each positioning element 720 and the outer surface ofstent 702 and as a result, the total rotation or bending of positioningelements 720 in the final deployed configuration may be less than 180degrees with respect to the initial distally-extending compressedconfiguration.

Rotating from the initial distally-extending configuration to the finalproximally-extending configuration allows valve prosthesis 700 to bedeployed in the annulus of the native mitral valve rather than theoutflow side of the native mitral valve, thereby minimizing the lengthwhich the prosthesis and the delivery system protrudes into the leftventricle. More particularly, prior art approaches for delivering avalve prosthesis include initially loading positioning or anchoringelements into the delivery system as proximally-extending, such that thepositioning elements are pressed against the stent of the valveprosthesis. Such initially proximally-extending positioning elementsflare outward or away from the stent less than ninety degrees whenreleased from a delivery sheath to a final deployed configuration. Inorder to properly position positioning elements that initially extend ina proximal direction at a mitral valve location, the valve prosthesiswould need to be distally extended past the native mitral valve and intothe left ventricle prior to retraction of the delivery sheath in orderto provide ample space for the positioning elements to deploy. After thepositioning elements flared to the acutely angled deployedconfiguration, the prosthesis would be proximally retracted in order tobring the positioning elements into contact with the native mitralvalve. However, in embodiments hereof, since positioning elements areinitially loaded into delivery system 730 as distally-extending, valveprosthesis 700 is initially positioned in the annulus of the nativemitral valve with only distally-extending positioning elements 720extending into the left ventricle prior to retraction of the deliverysheath.

In addition, the fact that positioning elements 720 are deployable viaone delivery sheath helps accommodate deployment of valve prosthesis 700at a native mitral valve despite constraints or considerations ofdelivering a prosthesis in a left ventricle. In some aortic valveapplications, multiple tubes are utilized for deploying stented cardiacvalve prosthetics. For example, the ENGAGER device from Medtronic, Inc.of Minneapolis, Minn. is a stented cardiac valve prosthesis havingpositioning elements in which two tubes are utilized for deployment. Afirst distal cone or tube is distally advanced into the aorta duringdeployment to deploy the positioning elements and then a second proximalsleeve is proximally retracted to deploy stent frame. However, whendeploying a valve prosthesis at a mitral valve target location, distallyadvancing a tube or sheath into the left ventricle may damage chordaetendineane located within the heart and/or may obstruct the leftventricular outflow tract (LVOT). In addition, the mitral valve ispositioned lower in the heart than the aortic valve and thus there isnot as much depth/length to distally advance a tube or sheath into theleft ventricle. Accordingly, valve prosthesis 700 is deployed viadelivery system 730 that includes only one delivery sheath 734 which isproximally retracted.

In order to transform between the initial distally-extending compressedconfiguration and the final proximally-extending deployed configuration,positioning elements according to embodiments described herein areformed from a self-expanding material that has a mechanical memory toreturn to the proximally-extending deployed configuration. For example,the positioning elements may be made from stainless steel, apseudo-elastic metal such as a nickel titanium alloy or Nitinol, or aso-called super alloy, which may have a base metal of nickel, cobalt,chromium, or other metal. As described above with respect to stent 102,mechanical memory may be imparted to the wire or tubular structure thatforms the positioning elements by thermal treatment to achieve a springtemper in stainless steel, for example, or to set a shape memory in asusceptible metal alloy, such as nitinol, or a polymer.

As previously described, each positioning element is coupled to thedistal end of the valve prosthesis. In one embodiment, each positioningelement may be coupled to the stent at multiple connection points. Morespecifically referring to FIG. 1A, U-shaped support arm 122A is coupledto distal end 104 of stent 102 via two V-shaped connectors 124A, 125Asuch that four connection points 126A, 127A, 128A, 129A are locatedbetween each positioning element 120 and stent 102. Similarly, shown inthe view of FIG. 14, U-shaped support arm 122B is coupled to distal end104 of stent 102 via two V-shaped connectors 124B, 125B such that fourconnection points 126B, 127B, 128B, 129B are located between eachpositioning element 120 and stent 102. In one embodiment, the eightconnection points 126A, 127A, 128A, 129A, 126B, 127B, 128B, 129B areapproximately equally spaced around the perimeter of distal end 104 ofstent 102 and collectively function to prevent the prosthetic valveleaflets from obstructing the outflow end of valve prosthesis 100 andthe left ventricular outflow tract (LVOT). Stated another way, V-shapedconnectors 124A, 125A, 124B, 125B increase the number of connectionpoints between each support arm 120A, 120B, respectively, and stent 102,and thereby shorten or minimize the open space or distance betweenadjacent connection points. V-shaped connectors 124A, 125A, 124B, 125Bact as an obstacle in the path that the prosthetic valve leaflets wouldfollow when overlapping onto stent 102 and thereby keeps the flow pathclear. Although described as “V-shaped connectors,” it will be apparentto those of ordinary skill in the art that two straight componentsformed generally in the shape of a “V” may be utilized in embodimentshereof rather than one single V-shaped component. In addition, althoughdescribed with respect to positioning elements 120 and stent 102, suchconnectors may be utilized for forming multiple connection pointsbetween any embodiment described herein, including positioning elements320 and stent 302, and position elements 720 and stent 702.

In one embodiment, positioning elements 120 and stent 102 are formed asan integral unitary structure, such as by laser cutting or etching thepositioning elements and stent from a single hollow tube or sheet. Inanother embodiment, V-shaped connectors 124A, 124B and/or U-shapedsupport arms 122A, 122B, may be separate components that are formedseparately and mechanically coupled to each other and to stent 102 viaany suitable mechanical method, including welding, soldering, or byanother mechanical method.

In order to lower the amount of stress and/or strain that occurs inV-shaped connectors 124A, 125A, 124B, 125B as positioning elements 120transform between the initial distally-extending compressedconfiguration and the final proximally-extending deployed configuration,the width of the wire(s) or tubular member(s) which form V-shapedconnectors 124A, 125A, 124B, 125B may be increased as compared to thewidth or dimension of U-shaped support arms 122A, 122B as well ascompared to the width or dimension of the wire or tubular member whichforms stent 102. More particularly, FIG. 15 illustrates a sectional viewalong line X-X of FIG. 14 showing a strut 123B of V-shaped connector124B according to one embodiment hereof. A reference width W_(R) isshown in phantom in FIG. 15 and represents the width of the wire ortubular member which forms stent 102 and/or U-shaped support arms 122A,122B. A width W_(S) of strut 123B is widened or increased relative towidth W_(R), thereby increasing the amount of material of V-shapedconnector 124B such that it can handle the deformation that occursthereto during deployment of valve prosthesis 100. In order to widen orincrease the width of strut 123B, material may be added or banded tostrut 123B around the width direction thereof. In an embodiment,material may be added to include the width of strut 123B up to threetimes of width W_(R). Preferably, a thickness T_(S) of strut 123B is notincreased relative to the thickness of the wire or tubular member whichforms stent 102 due to size constraints on the compressed outer diameteror profile of valve prosthesis 100 when in the compressed configuration.As utilized herein, thickness T_(S) of strut 123B refers to the strutmaterial that extends in a radial direction relative to stent 102.Although illustrated as constant or uniform, thickness T_(S) of strut123B may vary or increase from an inner surface relative to an outersurface of strut 123B.

FIGS. 16-20 illustrate a method of delivering and implanting stentmitral valve prosthesis 100 in accordance with an embodiment hereof toperform a heart valve replacement procedure, more particularly a mitralvalve replacement, with minimal blood flow stoppage or interruption.FIG. 16 illustrates a portion of a heart H including a left atrium LA, aleft ventricle LV, a mitral valve space MV and an aortic valve AV. Bloodflow BF is depicted with directional arrows in FIG. 16 in the leftatrium LA, into left ventricle LV through mitral valve space MV, andinto the aorta through aortic valve AV. When the native mitral valve isoperating properly, the native leaflets will generally function in sucha way that blood flows toward the left ventricle LV when the leafletsare in an open position, and so that blood is prevented from movingtoward the left atrium LA when the leaflets are in a closed position.However, a valve prosthesis in accordance with an embodiment hereof canbe positioned in the area of mitral valve MV when it is not functioningproperly (to replace the mitral valve) in accordance with the invention,thereby pushing the native leaflets out of the mitral valve space.

With reference to FIG. 16, a prosthetic valve delivery system 1630 isshown after having been introduced into the vasculature via apercutaneous entry point, a.k.a the Seldinger technique, and having beentracked through the vasculature and into the left atrium so that distaltip 1640 is positioned proximate the mitral valve. For example, thepercutaneous entry point may be formed in a femoral vein. Thereafter, aguidewire (not shown) is advanced through the circulatory system,eventually arriving at the heart. The guidewire is directed into theright atrium, traverses the right atrium and is made to puncture withthe aid of a transeptal needle or pre-existing hole, the atrial septum,thereby entering the left atrium. Once the guidewire is positioned, theendoluminal entry port and the atrial septum are dilated to permit entryof a guide catheter (not shown) and/or prosthetic valve delivery system1630 into the left atrium. Thereafter, prosthetic valve delivery system1630 is advanced into the left atrium through the punctured atrialseptum and positioned proximate to the mitral valve MV. Although notshown, it will be understood by those of ordinary skill in the art thatprosthetic valve delivery system 1630 may be inserted into a guidecatheter in order to be advanced to a position proximate to the mitralvalve MV. In addition, although described as a transfemoral antegradeapproach for percutaneously accessing the mitral valve, the valveprosthesis 100 may be positioned within the desired area of the heartvia entry other different methods such as a transseptal antegradeapproach via a thoracotomy for accessing the mitral valve.

Similar to delivery system 730 described above with respect to FIGS. 7A,7B and 8-13, prosthetic valve delivery system 1630 includes an outerretractable sheath or tube 1634 positioned over the a catheter (notshown in FIGS. 16-20) having compressed valve prosthesis 100 to keep itfrom expanding and to minimize interference between the valve prosthesisand the vasculature through which it will be traveling. Valve prosthesis100 is mounted over an inner shaft of the catheter at the distal endthereof and sheath 1634 surrounds and constrains valve prosthesis 100 inthe compressed configuration. After being advanced into the left atriumLA, prosthetic valve delivery system 1630 including sheath 1634 may thenbe advanced through the mitral valve MV and into the left ventricle LVas shown in FIG. 17. Distal tip 1640 of prosthetic valve delivery system1630 is advanced into the left ventricle LV until valve prosthesis 100is centered at the native mitral valve, i.e., deployed in the annulus ofthe native mitral valve, with positioning elements 120 of valveprosthesis 100 contained within sheath 1634 and distally extending intothe left ventricle LV. As previously discussed, deploying valveprosthesis 100 in the middle of the native valve rather than the outflowside of the native mitral valve minimizes the length which theprosthesis and the delivery system protrudes into the left ventricle.

Referring now to FIG. 18, when valve prosthesis 100 is in position inthe middle of the native mitral valve, positioning elements 120 of valveprosthesis 100 are released by retracting sheath 1634 of prostheticvalve delivery system 1630 by a sufficient amount that this portion ofthe prosthesis is exposed. Due to the self-expanding properties of thepositioning elements, support arms 122A, 122B will expand radiallyoutwardly relative to the sheath in which it was enclosed. As shown FIG.18, and also referring to FIG. 8 described above, upon initial releasefrom sheath 1634, positioning elements 120 flare or spread outwardlyfrom the outer surface of the remainder of the prosthesis such thatpositioning elements 120 are acutely angled with respect to longitudinalaxis L_(a). During the transformation between the distally-extendingcompressed configuration and the proximally-extending deployedconfiguration, support arms 122A, 122B are located on outflow side,i.e., the left ventricle LV side, of the mitral valve while stent 102 ofprosthesis 100 is positioned within the mitral valve and still containedwithin sheath 1634.

Exposure and rotation of positioning elements 120 continues as sheath1634 is retracted. FIG. 19 illustrates positioning elements 120 fullyexposed or released from sheath 1634 while stent 102 is still compressedwithin sheath 1634. Positioning elements 120 are now proximallyextending, and support arms 122A, 122B firmly press against the nativemitral valve leaflets and/or the left ventricle LV in order to positionvalve prosthesis 100.

After positioning elements 120 are deployed to anchor or hold valveprosthesis 100 in place as desired, sheath 1634 continues to beproximally retracted, exposing self-expanding stent 102 such that stent102 is released from the delivery system to assume its deployedconfiguration. Due to the self-expanding properties of the stent frame,stent 102 will expand outwardly relative to the sheath in which it wasenclosed. Sheath 1634 is proximally retracted until the proximal end ofstent 102 is exposed and allowed to self-expand, thereby uncoupling theprosthesis from catheter 1632. The delivery system can then be refractedfrom the patient, leaving the expanded prosthesis 100 deployed at themitral valve as shown in FIG. 20. In the final deployed configuration ofvalve prosthesis 100, each positioning element 120 proximally extendsfrom a distal end 104 of stent 102. Each positioning element 120 rotatesin a radial direction between 90 and 180 degrees from the initialdistally-extending compressed configuration to the finalproximally-extending deployed configuration until support arms 122A,122B firmly press against the native mitral valve leaflets and/or theleft ventricle LV in order to position valve prosthesis 100. The amountor degree of rotation may depend upon a patient's individual anatomy andstate of the native mitral valve leaflets.

FIGS. 21A, 21B, 22A, 22B illustrates another embodiment of positioningelements with double or dual support arms that may be utilized in anyembodiment described herein. More particularly, a valve prosthesis 2100is shown in its compressed or delivery configuration in the side viewsof FIG. 21A and FIG. 21B and in its expanded or deployed configurationin the side views of FIG. 22A and FIG. 22B. Similar to embodimentsdescribed above, valve prosthesis 2100 includes a framework or stent2102, a valve component 2116 attached within the interior portion ofstent 2102 that is capable of blocking flow in one direction to regulateflow through valve prosthesis 2100 via leaflets 2118A, 2118B, and twopositioning elements 2120. Stent 2102 of valve prosthesis 2100 is agenerally tubular expandable body having a stepped outer diameter orprofile extending between a proximal end 2106 and distal end 2104.Similar to embodiments described above, the stepped outer diameter ofstent 2102 includes a distal or ventricular segment 2108 and a proximalor atrial segment 2110 having an expanded diameter which is greater thanthe expanded diameter of distal segment 2108.

Positioning elements 2120 extend from opposing sides of stent 2102. Eachpositioning element 2120 includes a first or outer U-shaped support arm2140A, 2140B, respectfully, and a second or inner U-shaped support arm2142A that each distally extend from a distal end 2104 of stent 2102.The second or inner U-shaped support arm adjacent to outer U-shapedsupport arm 2140B is obscured from view in the figures, but it will beunderstood by those of ordinary skill in the art that each positioningelement 2120 includes both an outer U-shaped support arm and an innerU-shaped support arm. When released from a delivery sheath (not shown),each of the U-shaped support arms gradually bends outwardly and thentowards an outer surface of the delivery device or stent until theytransform from their compressed configuration of FIG. 21A and FIG. 21Bto their deployed configuration of FIG. 22A and FIG. 22B in which eachof the U-shaped support arms proximally extends from distal end 2104 ofstent 2102. As in embodiments described above, each of the U-shapedsupport arms bends or rotates more than ninety degrees with respect toits compressed, delivery configuration during deployment of valveprosthesis 2100. In one embodiment, each U-shaped support arm rotatesbetween 135 degrees and 180 degrees during deployment of valveprosthesis 2100. Compared to a single U-shaped support arm, outer andinner U-shaped support arms provide each positioning element 2120 withadditional spring force for improved anchoring and positioning of thevalve prosthesis.

Adjacent outer and inner U-shaped support arms of each positioningelement are coupled together via a connector 2144A which ensures thatboth U-shaped support arms of the positioning element remain in the sameplane during deployment. Connector 2144A has a flared V-shapedconfiguration in which an apex 2145 of connector 2144A is coupled to apeak or crest 2143 of inner support arm 2142A. More particularly,connector 2144A includes two curved legs 2146A, 2146B. First ends oflegs 2146A, 2146B are coupled to peak 2143 of inner support arm 2142A,and curved legs 2146A, 2146B of connector 2144A extend or flare awayfrom each other such that second ends of legs 2146A, 2146B are coupledadjacent to or on opposing sides of a peak or crest 2141 of outersupport arm 2140A. Due to the curved legs 2146A, 2146B of connector2144A, the distance or space between the crowns of outer and innerU-shaped support arms is adjustable and allowed to change. Legs 2146A,2146B allow the distance or space between peak 2143 of inner support arm2142A and peak 2141 of outer support arm 2140A because the curved legsof connector 2144A may bend, resulting in a shorter distance betweenpeak 2143 and peak 2141, or the legs of connector 2144A may straighten,resulting in a greater distance between peak 2143 and peak 2141. Thedistance or space between peak 2143 and peak 2141 may increase duringcrimping when valve prosthesis 2100 is in its compressed configurationshown in FIG. 21A, 21B, and the distance or space may decrease duringexpansion when valve prosthesis 2100 is in its deployed configuration.Connector 2144A, as well as the inner and outer U-shaped support arms,may be laser cut from a tube of self-expanding material and therebyintegrally formed as part of the stent, or may be formed separately andsubsequently attached to the stent. Although connector 2144A is onlyvisible in FIGS. 21A, 21B, 22A, 22B between inner support arm 2142A andouter support arm 2140A, it will be understood by those of ordinaryskill in the art that such a connector couples the outer and innersupport arms of each positioning element extending from the prosthesis.

FIGS. 23A, 23B, 23C illustrate an embodiment of a valve prosthesis 2300including a lattice framework or stent 2302 and positioning elements2320 with dual U-shaped support arms that distally extend from a distalend 2304 of the valve prosthesis. More particularly, positioningelements 2320 include a first or outer U-shaped support arm 2340A,2340B, respectfully, and a second or inner U-shaped support arm 2342A,2342B that each bend or rotate more than ninety degrees with respect toits compressed, delivery configuration during deployment. Each outersupport arm is connected to its respective inner support arm via aconnector 2344A, as described above with respect to connector 2144A. Inthe embodiment of FIGS. 23A, 23B, 23C, the U-shaped support arms extendfrom the distalmost crowns or apexes 2353 of lattice stent 2302.Compared to the embodiment shown in FIGS. 24A-24C, stent 2302 has asmaller crimped profile for delivery.

FIGS. 24A, 24B, 24C illustrate an embodiment of a valve prosthesis 2400that is similar to valve prosthesis 2300, except that positioningelements 2420 do not extend from distalmost crowns or apexes 2453 of alattice stent 2402. Rather, the positioning elements extend from betweenthe distalmost crowns or apexes 2453 of lattice stent 2402. As bestshown in FIG. 24B, in order to shorten or minimize the open space ordistance 2450 between adjacent positioning elements 2420, positioningelements 2420 extend from opposing sides of a distalmost crown 2453 suchthat the positioning elements are separated only by the width of thecrown. More particularly, positioning elements 2420 distally extend froma distal end 2404 of the valve prosthesis and include a first or outerU-shaped support arm 2440A, 2440B, respectfully, and a second or innerU-shaped support arm 2442A, 2442B that each bend or rotate more thanninety degrees with respect to its compressed, delivery configurationduring deployment. Each outer support arm is connected to its respectiveinner support arm via a connector 2444A, as described above with respectto connector 2144A. Positioning elements 2420 extend from between thedistalmost crowns or apexes 2453 of lattice stent 2402 to minimize openspace or distance 2450 and thereby prevent the prosthetic valve leafletsfrom obstructing the outflow end of valve prosthesis 2400 and the leftventricular outflow tract (LVOT). Outer U-shaped support arms of thepositioning elements are closer together, and act as an obstacle in thepath that the prosthetic valve leaflets would follow when overlappingonto stent 2402 and thereby keeps the flow path clear. Another benefitof extending positioning elements 2420 from between the distalmostcrowns or apexes 2453 of lattice stent 2402 is that the positioningelements are located more proximal along the prosthesis compared to theembodiment shown in FIGS. 23A-23C, which minimizes the length or amountof material that projects or extends in the left ventricle.

FIGS. 25A and 25B illustrate another embodiment of a valve prosthesis2500 that is similar to valve prosthesis 2400, except that eachpositioning element 2520 includes triple support arms for additionalspring force for improved anchoring and positioning of the valveprosthesis. Each positioning element 2520 extends from between thedistalmost crowns of a distal end 2504 of a lattice stent 2502 andincludes a first or outer U-shaped support arm 2540A, a second orintermediate U-shaped support arm 2542A, and a third or inner U-shapedsupport arm 2554A. When released from a delivery sheath (not shown inFIG. 25A or FIG. 25B), all of the U-shaped support arms gradually bendoutwardly and then towards an outer surface of the delivery device orstent until they reach their deployed configuration of FIG. 25A and FIG.25B in which all of the U-shaped support arms proximally extend fromdistal end 2504 of stent 2502. As in embodiments described above, all ofthe U-shaped support arms bend or rotate more than ninety degrees withrespect to its compressed, delivery configuration during deployment ofvalve prosthesis 2500. In one embodiment, each U-shaped support armrotates between 135 degrees and 180 degrees during deployment of valveprosthesis 2100. Although only one positioning element is shown indescribed in FIGS. 25A, 25B, it will be understood by those of ordinaryskill in the art that valve prosthesis 2500 includes at least twopositioning elements extending from opposing sides of the prosthesis.Each positioning element includes triple U-shaped support arms foranchoring and positioning the valve prosthesis.

Adjacent U-shaped support arms of each positioning element are coupledtogether via a connector which ensures that each support arm of thepositioning element remains in the same plane during deployment. Morespecifically, outer U-shaped support arm 2540A is coupled tointermediate U-shaped support arm 2542A via a connector 2544A andintermediate U-shaped support arm 2542A is coupled to inner U-shapedsupport arm 2554A via a connector 2556A. Connectors 2544A, 2556A havethe same flared V-shaped configuration as connector 2144A describedabove. Due to the curved or flared legs of connectors 2544A, 2556A, thedistance or space between the peaks of adjacent U-shaped support arms isadjustable and allowed to change as described with respect to connector2144A.

While various embodiments according to the present invention have beendescribed above, it should be understood that they have been presentedby way of illustration and example only, and not limitation. It will beapparent to persons skilled in the relevant art that various changes inform and detail can be made therein without departing from the spiritand scope of the invention. For example, although support arms ofvarious embodiments are described herein as U-shaped, it will beunderstood by one of ordinary skill in the art that any support armdescribed herein may be generally U-shaped or V-shaped as shown in FIGS.26A-26F. In addition, valve prostheses described here may include morethan two positioning elements that transform from an initialdistally-extending compressed configuration to a finalproximally-extending deployed configuration. A minimum of twopositioning elements are required such that a support arm is positionedbehind each leaflet of a native mitral valve. However, additionalpositioning elements may be included without departing from the spiritand scope of the invention. In one embodiment, four positioning elementsmay be circumferentially disposed around the perimeter of a stent thatsupports a prosthetic bileaflet valve therein. In another embodiment,three positioning elements may be circumferentially disposed around theperimeter of a stent that supports a prosthetic trileaflet valvetherein.

In addition to variations of the positioning elements, various changesin form and detail can be made to the stent of the valve prosthesiswithout departing from the spirit and scope of the invention. Aspreviously described, the stent frame may have any suitableconfiguration known in the art. In addition, although not required,portions of the stent may be selectively plated with platinum or otherbiocompatible material to provide improved visibility during fluoroscopyand thereby aid in positioning the stent in the middle of the mitralvalve for deployment. In one embodiment of the present invention, one ormore radiopaque markers (not shown) may be attached to the valveprosthesis at one or more predetermined locations. The marker may beformed of platinum or any other relatively heavy metal, which may begenerally visible by X-ray fluoroscopy.

Accordingly, the breadth and scope of the present invention should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the appended claims and theirequivalents. It will also be understood that each feature of eachembodiment discussed herein, and of each reference cited herein, can beused in combination with the features of any other embodiment. Allpatents and publications discussed herein are incorporated by referenceherein in their entirety.

What is claimed is:
 1. A heart valve prosthesis comprising: a tubularstent having a compressed configuration for delivery within avasculature and a deployed configuration for deployment within a nativeheart valve; a prosthetic valve component disposed within and secured tothe stent; and at least two positioning elements coupled to a distal endof the stent to position and anchor the prosthesis within the nativeheart valve, each positioning element including an outer generallyU-shaped or V-shaped support arm and an inner generally U-shaped orV-shaped support arm that both distally extend from the distal end ofthe stent when the stent is in the compressed configuration, eachgenerally U-shaped or V-shaped support arm having a first end and asecond end coupled to the distal end of the stent with a peak formedbetween the first and second ends, the outer and inner support armsextending along the same plane and the inner support arm being disposedwithin the outer support arm such that the peaks of the inner and outersupport arms are aligned, and such that each of the first and secondends of the outer support arm is coupled to the stent at acircumferentially spaced apart location from the respective first andsecond ends of the inner support arm, wherein during deployment of theprosthesis each support arm bends radially outward and then towards anouter surface of the stent such that it translates more than ninetydegrees from the compressed configuration to proximally extend from thedistal end of the stent when the stent is in the deployed configuration,and wherein a connector extends from the peak of the outer support armto the peak of inner support arm and couples the peaks of the supportarms together to ensure that the support arms remain in the same planeduring deployment of the prosthesis.
 2. The heart valve prosthesis ofclaim 1, wherein each positioning element is approximately parallel witha longitudinal axis of the stent and distally extends from the distalend of the stent when the stent is in the compressed configuration. 3.The heart valve prosthesis of claim 2, wherein each positioning elementrotates in a radial direction between 135 degrees and 180 degrees fromthe compressed configuration during deployment of the prosthesis.
 4. Theheart valve prosthesis of claim 1, wherein the stent has a steppedprofile including a distal ventricular portion having a first expandeddiameter and a proximal atrial portion having a second expanded diameterwhich is greater than the first expanded diameter.
 5. The heart valveprosthesis of claim 1, wherein the stent and the positioning elementsare formed as a unitary structure.
 6. The heart valve prosthesis ofclaim 1, wherein the prosthetic valve component includes two leaflets.7. The heart valve prosthesis of claim 1, wherein the connector thatcouples the peaks of the support arms together includes two curved legs,wherein first ends of the curved legs extend from the peak of the innersupport arm and the curved legs flare away from each other such thatsecond ends of the curved legs extend from opposing sides of the peak ofthe outer support arm.
 8. The heart valve prosthesis of claim 1, whereineach support arm extends from distalmost crowns of the stent.
 9. Theheart valve prosthesis of claim 1, wherein each support arm extends frombetween distalmost crowns of the stent.
 10. The heart valve prosthesisof claim 1, wherein each positioning element includes an intermediateU-shaped or V-shaped support arm between the outer support arm and theinner support arm, the intermediate support arm having a first end and asecond end coupled to the distal end of the stent with a peak formedbetween the first and second ends.
 11. A heart valve prosthesiscomprising: a tubular stent having a compressed configuration fordelivery within a vasculature and a deployed configuration fordeployment within a native heart valve; a prosthetic valve componentdisposed within and secured to the stent; and at least two positioningelements coupled to a distal end of the stent to position and anchor theprosthesis within the native heart valve, wherein each positioningelement distally extends from the distal end of the stent when the stentis in the compressed configuration and proximally extends from thedistal end of the stent when the stent is in the deployed configuration,each positioning element including an outer support arm having a firstend and a second end coupled to the distal end of the stent with a peakformed between the first and second ends and an inner support arm havinga first end and a second end coupled to the distal end of the stent witha peak formed between the first and second ends, the outer and innersupport arms extending along the same plane and the inner support armbeing disposed within the outer support arm such that the peaks of theinner and outer support arms are aligned and each of the first andsecond ends of the outer support arm is coupled to the stent at acircumferentially spaced apart location from the respective first andsecond ends of the inner support arm, wherein the peak of the outersupport arm is coupled to the peak of the inner support arm via aconnector to ensure that the support arms remain in the same planeduring deployment of the prosthesis.
 12. The heart valve prosthesis ofclaim 11, wherein each support arm is generally U-shaped or V-shaped.13. The heart valve prosthesis of claim 11, wherein during deployment ofthe prosthesis each support arm bends radially outward and then towardsan outer surface of the stent such that it translates between 135degrees and 180 degrees from the compressed configuration to proximallyextend from the distal end of the stent when the stent is in thedeployed configuration.
 14. The heart valve prosthesis of claim 13,wherein each positioning element is approximately parallel with alongitudinal axis of the stent and distally extends from the distal endof the stent when the stent is in the compressed configuration.
 15. Theheart valve prosthesis of claim 11, wherein the stent and thepositioning elements are formed as a unitary structure.
 16. The heartvalve prosthesis of claim 11, wherein the connector includes two curvedlegs, the first ends of the legs extending from the peak of the innersupport arm and flaring away from each other such that second ends ofthe legs extend from opposing sides of the peak of the outer supportarm.
 17. The heart valve prosthesis of claim 11, wherein eachpositioning element also includes an intermediate support arm having afirst end and a second end coupled to the distal end of the stent with apeak formed between the first and second ends, the intermediate supportarm extending along the same plane as the outer and inner support armsand being disposed between the outer support arm and the inner supportarm such that the peaks of the inner, outer, and intermediate supportarms are aligned.